A battery is generally used in mobile devices such as a mobile phone and a personal digital assistant (PDA). As a battery most commonly used in the mobile devices, a lithium ion battery is heated when overcharge or overcurrent occurs, and even has the risk of explosion as well as performance degradation if heating is continued and thus temperature thereof is increased. Accordingly, a typical battery includes a protection circuit module for detecting and blocking overcharge, overdischarge, and overcurrent, or uses an external protection circuit for detecting overcharge, overdischarge, or heating and blocking operation of the battery. This conventional protection circuit is generally produced by soldering a protection integrated circuit (IC), a field effect transistor (FET), resistors, capacitors, etc. on a printed circuit board (PCB). However, the conventional protection circuit may not easily achieve a small size because the protection IC, the FET, the resistors, and the capacitors occupy an excessively large space. Furthermore, an additional process is required to mount the protection circuit in a battery pack. After the protection circuit is mounted, a process for additionally connecting external connection terminals or internal connection terminals thereof through wires, wire bonding, the pattern of the PCB, or exposed terminals of the PCB is complicated.